U.S. officials concerned over North Korea's 'ratcheting up of rhetoric'

By K.J. Kwon. Jethro Mullen and Pam Benson, CNN

Updated 8:53 AM ET, Thu March 28, 2013

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Photos:Kim Jong Un and North Korea's military

North Korean leader Kim Jong Un meets with North Korea's first female fighter jet pilots in this undated photo released by the country's state media on Monday, June 22. He called the women "heroes of Korea" and "flowers of the sky."

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Photos:Kim Jong Un and North Korea's military

Kim stands on the snow-covered top of Mount Paektu in North Korea in a photo taken by North Korean newspaper Rodong Sinmun on April 18 and released the next day by South Korean news agency Yonhap. Kim scaled the country's highest mountain, North Korean state-run media reported, arriving at the summit to tell soldiers that the hike provides mental energy more powerful than nuclear weapons.

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Kim Jong Un, center, poses with soldiers on the snow-covered top of Mount Paektu in an April 18 photo released by South Korean news agency Yonhap.

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Kim visits the Kumsusan Palace of the Sun in Pyongyang, North Korea, on April 15 to celebrate the 103rd birth anniversary of his grandfather, North Korean founder Kim Il Sung.

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Kim inspects a drill for seizing an island at an undisclosed location in North Korea in an undated picture released by North Korea's official Korean Central News Agency on February 21.

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Kim speaks during a meeting of the Political Bureau of the Central Committee of the Workers' Party of Korea in Pyongyang, North Korea, in this photo released February 19 by the state-run Korean Central News Agency.

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Photos:Kim Jong Un and North Korea's military

A picture released by the North Korean Central News Agency shows North Korean leader Kim Jong Un appearing without his cane at an event with military commanders in Pyongyang on Tuesday, November 4. Kim, who recently disappeared from public view for about six weeks, had a cyst removed from his right ankle, a lawmaker told CNN.

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Kim is seen walking with a cane in this image released Thursday, October 30, by the state-run Korean Central News Agency.

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Kim sits in the pilot's seat of a fighter jet during the inspection.

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This undated photo, released Tuesday, October 14, by the KCNA, shows Kim inspecting a housing complex in Pyongyang, North Korea. International speculation about Kim went into overdrive after he failed to attend events on Friday, October 10, the 65th anniversary of the Workers' Party. He hadn't been seen in public since he reportedly attended a concert with his wife on September 3.

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A picture released by the KCNA shows Kim and his wife watching a performance by the Moranbong Band on Wednesday, September 3, in Pyongyang.

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Kim tours a front-line military unit in this image released Wednesday, July 16, by the KCNA.

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Kim poses for a photo as he oversees a tactical rocket-firing drill in June.

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Kim watches a tactical rocket-firing drill in June.

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A North Korean soldier patrols the bank of the Yalu River, which separates the North Korean town of Sinuiju from the Chinese border town of Dandong, on Saturday, April 26.

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In this photo released Thursday, April 24, by the Korean Central News Agency, Kim smiles with female soldiers after inspecting a rocket-launching drill at an undisclosed location.

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A picture released Tuesday, March 18, by the KCNA shows Kim attending a shooting practice at a military academy in Pyongyang.

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A North Korean soldier uses binoculars on Thursday, February 6, to look at South Korea from the border village of Panmunjom, which has separated the two Koreas since the Korean War.

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A North Korean soldier kicks a pole along the banks of the Yalu River on Tuesday, February 4.

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A photo released by the KCNA on Thursday, January 23, shows the North Korean leader inspecting an army unit during a winter drill.

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Kim inspects the command of an army unit in this undated photo released Sunday, January 12, by the KCNA.

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Kim visits an army unit in this undated photo.

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Kim inspects a military factory in this undated picture released by the KCNA in May 2013.

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Kim visits the Ministry of People's Security in 2013 as part of the country's May Day celebrations.

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A North Korean soldier, near Sinuiju, gestures to stop photographers from taking photos in April 2013.

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North Korean soldiers patrol near the Yalu River in April 2013.

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Kim is briefed by his generals in this undated photo. On the wall is a map titled "Plan for the strategic forces to target mainland U.S."

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Kim works during a briefing in this undated photo.

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In this KCNA photo, Kim inspects naval drills at an undisclosed location on North Korea's east coast in March 2013.

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Kim, with North Korean soldiers, makes his way to an observation post in March 2013.

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Kim uses a pair of binoculars to look south from the Jangjae Islet Defense Detachment, near South Korea's Taeyonphyong Island, in March 2013.

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Kim is greeted by a soldier's family as he inspects the Jangjae Islet Defense Detachment in March 2013.

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Kim is surrounded by soldiers during a visit to the Mu Islet Hero Defense Detachment, also near Taeyonphyong Island, in March 2013.

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Kim arrives at Jangjae Islet by boat to meet with soldiers of the Jangjae Islet Defense Detachment in March 2013.

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Soldiers in the North Korean army train at an undisclosed location in March 2013.

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In a photo released by the official North Korean news agency in December 2012, Kim celebrates a rocket's launch with staff from the satellite control center in Pyongyang.

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Kim, center, poses in this undated picture released by North Korea's official news agency in November 2012.

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Kim visits the Rungna People's Pleasure Ground, under construction in Pyongyang, in a photo released in July 2012 by the KCNA.

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A crowd watches as statues of North Korean founder Kim Il Sung and his son Kim Jong Il are unveiled during a ceremony in Pyongyang in April 2012.

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A North Korean soldier stands guard in front of an UNHA III rocket at the Tangachai-ri Space Center in April 2012.

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In April 2012, Pyongyang launched a long-range rocket that broke apart and fell into the sea. Here, the UNHA III rocket is pictured on its launch pad in Tang Chung Ri, North Korea.

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– A closer look at the UNHA III rocket on its launch pad in Tang Chung Ri, North Korea.

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A military vehicle participates in a parade in Pyongyang in April 2012.

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North Korean soldiers relax at the end of an official ceremony attended by leader Kim Jong Un at a stadium in Pyongyang in April 2012.

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Kim Jong Un applauds as he watches a military parade in Pyongyang in April 2012.

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A North Korean soldier stands on a balcony in Pyongyang in April 2012.

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North Korean soldiers march during a military parade in Pyongyang in April 2012.

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Soldiers board a bus outside a theater in Pyongyang in April 2012.

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North Korean performers sit below a screen showing images of leader Kim Jong Un in Pyongyang in April 2012.

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North Korean soldiers salute during a military parade in Pyongyang in April 2012.

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North Korean soldiers listen to a speech during an official ceremony attended by leader Kim Jong Un at a stadium in Pyongyang in April 2012.

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Members of a North Korean military band gather following an official ceremony at the Kim Il Sung stadium in Pyongyang in April 2012.

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North Korean military personnel watch a performance in Pyongyang in April 2012.

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A North Korean controller is seen along the railway line between the Pyongyang and North Pyongan provinces in April 2012.

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A North Korean military honor guard stands at attention at Pyongyang's airport in May 2001.

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"What's not clear right now is how much risk (North Korean leader) Kim Jong Un is willing to run, to show the world and domestic elites that he's a tough guy. His inexperience is certain -- his wisdom is still very much in question."

North Korea earlier said it was cutting off a key military hotline with South Korea amid high tensions between the two sides.

"Under the situation where a war may break out any moment, there is no need to keep north-south military communications," the head of a North Korean delegation told the South by telephone Wednesday, according to the North's state-run Korean Central News Agency.

There are several hotlines between North and South Korea. Earlier this month, Pyongyang disconnected a Red Cross hotline that ran through the border village of Panmunjom and was used by officials on both sides, according to the South Korean Unification Ministry.

And senior U.S. officials do not believe the cutting off of some communication by North Korea in itself is indicative of more dramatic action or is conclusive. The officials note that North Korea has cut these links before, some of them multiple times.

"It's part of the current threat-of-the-day pattern. I wouldn't extrapolate it to anything more conclusive," one official said.

"They want attention and they want to scare people both inside and outside their country."

Officials see steps such as cutting off communication are more substitutes for doing other more dangerous things rather than precursors to more dangerous things.

At the same time, there is concern about a North Korean miscalculation during this time. The officials said the lack of communication could complicate and hamper the ability of all nations involved (including North Korea, South Korea and the United States) to control and moderate any action -- and cycle of reaction should one begin as the result of a North Korean miscalculation.

The North linked its move to annual joint military exercises by South Korea and the United States, which it has cited in a string of threats against the two countries in recent weeks. Tougher sanctions approved by the U.N. Security Council also may have fueled its anger.

"It is important the U.S. send a message. In terms of the military side, the U.S. has clearly sent a message," the intelligence official said. "When people engage in this sort of rhetoric, you can't appear as if you are not responding," the official said.

The intelligence community has been providing the Obama administration with assessments of Kim Jung Un's control of the regime, but the official would not provide any details of that assessment.

Josh Earnest, White House principal deputy press secretary, said the United States is committed to ensuring the security of its allies, such as South Korea.

"The North Koreans are not going to achieve anything through these threats and provocations. They're only going to further isolate the North Koreans and undermine international efforts to bring peace and stability to northeast Asia," Earnest said.

Pentagon spokesman George Little spoke on the government's nuclear threats to the United States and "its more achievable threats to attack South Korean military units and shell border islands."

"We take their rhetoric seriously, whether it's outside the norm which it sometimes is, or seems to suggest a more direct threat. And if you look at what they've said recently, it's been extremely provocative, threatening and bellicose. And it's a complete mystery to me why they would deem it in their own interest to launch this type of rhetoric at us and our allies," Little said.

The North's announcement Wednesday appeared likely to affect the movement of people in and out of the Kaesong Industrial Complex, a joint economic cooperation zone between the two Koreas situated on the North's side of the border.

"The measure taken by North Korea is not beneficial for the stable operation of the Kaesong Industrial Complex, and we urge them to withdraw the measure," the Unification Ministry said.

On Thursday morning, the day after the North said it was severing the line, South Korean workers were able to cross the border and enter the industrial zone, the semiofficial South Korean news agency Yonhap reported, citing the Immigration and Quarantine office in Paju, near the border.

An initial group of 197 workers went over the border at 8:30 a.m. local time (7:30 p.m. Wednesday ET) after North Korea gave the regular approval for their movement by phone through the industrial district's management committee, Yonhap said.

A total of 530 South Koreans were due to enter the Kaesong complex on Thursday, and 511 are scheduled to come back into South Korea, according to Yonhap.

A symbol of North-South cooperation, the Kaesong complex is also seen as an important source of hard currency for the regime in Pyongyang.

The North previously cut off the Kaesong military hotline in March 2009 -- also during annual U.S.-South Korean military exercises -- but later reinstated it, according to Yonhap.

The slew of recent fiery rhetoric from Pyongyang has included threats of pre-emptive nuclear strikes against the United States and South Korea, as well as the declaration that the armistice that stopped the Korean War in 1953 is no longer valid.

On Tuesday, the North said it planned to place military units tasked with targeting U.S. bases under combat-ready status.

Most observers say North Korea is still years away from having the technology to deliver a nuclear warhead on a missile, but it does have plenty of conventional military firepower, including medium-range ballistic missiles that can carry high explosives for hundreds of miles.

The heightened tensions on the Korean Peninsula came after the North carried out a long-range rocket launch in December and an underground nuclear test last month, prompting the U.N. Security Council to step up sanctions on the secretive regime.